The title may be a bit clunky, but the New Millennium/New Music series at the Chicago Cultural Center has developed into a major focal point for innovative ideas in sound. So it was fitting that the season finale of the series (which will resume in the fall) featured one of the most promising artists on Chicago's improvised music scene.

Though anyone who frequents venues such as the Empty Bottle or the 3030 performance space already is acquainted with saxophonist David Rempis' art, the set he turned in Wednesday night in the Cultural Center's Claudia Cassidy Theater suggested that he has attained a new level of technical command and expressive clarity. Leading the quartet that appears on his new CD, "Out of Season," Rempis offered profound introspection as well as incendiary virtuosity and carefully controlled phrase-making as well as passages of unbridled energy and drive.

Savvy performer that he is, Rempis opened the evening with some of the most muted, lustrous and lyrical playing one might hope to encounter from an avant-gardist of his youthful vintage. Choosing to disarm his listeners rather than accost them, Rempis unspooled long, singing phrases that addressed the ear gently.

Even so, this was not exactly easy listening, for Rempis was improvising lines that ventured far outside traditional Western harmony. The combination of Rempis' uncommonly plush tone, evocative vibrato and unabashedly non-chordal vocabulary produced a music as alluring and genteel as it was experimental and uninhibited.

Before long, however, Rempis and friends kicked up the energy level, particularly when the bandleader switched to alto saxophone. Producing high-register squeaks and squeals one moment and barely whispered riffs the next, Rempis vividly established that his music is too volatile to predict, too stylistically far-ranging to categorize and too intricate to put to paper. In some of Rempis' most rhythmically heated and sonically explosive passages, the band achieved more power and momentum than one might have thought possible from four musicians. With Baker churning out strange, other-worldly buzzes and beeps on synthesizer, Daisy setting off eruptions on drums and Roebke driving hard on bass, this band pushed hard at the outer limits of volume, ensemble density and rhythmic aggression. Not surprisingly, a few listeners left, presumably finding it all a bit overwhelming.

But for those willing to stick with it, Rempis played a set that yielded more musical ideas, complexity of thought and relentless invention than one typically encounters in a weeks' worth of concert-going. The man clearly is poised for a significant future, and - judging by this performance - he stands an excellent chance of making the most of it.